1. Field of the Invention
The present invention relates to a portable radio terminal with an infrared communication function and a communication method for the portable radio terminal with the infrared communication function and more particularly to the portable radio terminal with the infrared communication function and the communication method for the portable radio-terminal with the infrared communication function for power control when infrared communication and radio communication are executed simultaneously.
2. Description of the Related Art
A radio communication function transmits radio waves in order to carry out radio communications. Transmission power to transmit radio waves generally requires a large consumption of electric current (for example, an RCR STD-27 digital radiophone system, such as a PDC (Personal Digital Cellular) system, is used as a radio communication system).
An infrared communication function also requires a large consumption of electric current in order to make an emitting element emit.
Therefore, in a case that an infrared communication function is provided in a radio portable information terminal using a battery as a power source, when the battery voltage drops, it becomes impossible to use the radio communication function and the infrared communication function simultaneously.
A terminal is known, in which irrespective of the battery voltage, it is restricted to use the radio communication function and the infrared communication function simultaneously from the beginning in order to give a longer lifetime of the battery for the radio portable information terminal, and a battery capacity and a power source circuit are minimized.
In these known techniques, there are the following problems.
A first problem is that the radio communication function and the infrared communication function can not be used simultaneously. As its causes, the infrared communication function requires a large consumption electric current and a communicable distance of the infrared communication function is required to be kept at a constant distance or more.
A second problem is that a large battery capacity is required to use the radio communication function and the infrared communication function simultaneously and a battery becomes large in size. As its cause, both of the radio communication function and the infrared communication function require large consumption of electric current.
Therefore, it is desirable to control an increase of consumption electric of current when the radio communication function and the infrared communication function are executed simultaneously.